Obama's lead in those polls has varied between a dead heat with Romney and a 5-point lead, averaging to a little over a 2-point advantage for the Democrat.

While Ohio is trending blue, it's nowhere near a sure thing for either candidate. While Obama has consistently held a small edge in Ohio, even after his lackluster performance during the first presidential debate, RealClearPolitics gives him a margin less than 2 points.

Obama's good numbers in Ohio are the main reason he is doing so well in most estimates of the Electoral College count.

While Obama has trailed slightly behind Romney in many nationwide polls, he is performing well in important swing states.

As the Electoral College goes, so goes the presidency, and neither candidate has an easy road to the necessary 270 electoral votes without Ohio.

Both campaigns seem poised to grab enough swing states to put them within striking distance of 270. If Romney sweeps the South, taking Virginia, North Carolina and Florida, as seems likely, he will be 22 votes from winning.

Ohio's 18 electoral votes make up the largest share of the remaining 43 votes.

Ohio and any other state secures a win, while without Ohio, a candidate must sweep every other remaining swing state: Nevada, Colorado, Iowa and New Hampshire.

Granted, that sweep looks easier for Obama than Romney, but New Hampshire and Colorado are by no means sure things for the president.

If Romney takes Ohio, his chances of winning increase exponentially.

Of course, either candidate could play a strong offense by trying to take a state considered "safer" for their opponent.

I've predicted that Pennsylvania will be called for Obama soon, but it is still a potential Romney pickup. And the similarities in geography and culture between Pennsylvania and Ohio would likely carry over any success to Romney's fight in the latter state.

Obama has a similar opportunity in Florida and Virginia. A large military population and wide swaths of rural areas make the situation in Virginia more difficult for the president, but he is still polling very close to even there.

Florida has a large Latino population, which generally supports Obama, but older, more conservative voters in the state combine with a large Cuban-American population to make it a tough sell for Obama.

Over the next few days, we'll see if Obama's performance in the final presidential debate, which was held in Boca Raton, Fla., will help him there.

But these scenarios are just possibilities. Ohio will be a huge battle, and whoever emerges victorious will likely take the entire election at the same time.